#include <stdio.h>

int main()
{
	char S[11], a[26] = {0};
	fgets(S, 11, stdin);
	for (int i = 0; S[i]; i++) {
		int j = S[i]-'A';
		if (a[j] != 0) {
			puts("NO");
			return 0;
		}
		a[j] = 1;
	}
	puts("YES");
	return 0;
}